The present invention relates to a rotary control valve which is ideally suited for use in, but is not limited to, a power steering system for an automobile, truck, airplane or other vehicle.
A conventional control valve for a power steering system comprises a tubular sleeve and a cylindrical rotor which is disposed in the sleeve for relative sliding rotation. The conjugate surfaces of the sleeve and rotor are formed with grooves which control flow of hydraulic fluid between ports. The ports are connected to a pressurized hydraulic fluid source, a reservoir and the opposite ends of a power piston respectively in such a manner that rotation of a steering wheel and thereby the rotor relative to the sleeve and vehicle direction control members such as wheels from a neutral position causes one end of the power piston to be connected to the pressure source and the other end of the power piston to be connected to the reservoir. This creates a net force on the power piston in a direction such as to assist the steering effort.
However, a conventional control valve having right cylndrical components must be manufactured using machining. Although the main bodies of the sleeve and rotor may be formed in molds, the grooves must be machined and the bodies machined to remove flash created by two piece molds.